Glutamic acid recovery



April 19, 1960 F. A. HOGLAN GLUTAMIC ACID RECOVERY Filed Jam.V 2a, 1957 wie 70 -852 dry s/zds,

Orafzazry fern/a Crude fldfam'z acid frz/enfer:

United States Patent O GLUTAMIC ACID RECOVERY Forest A. Hoglan, Glenview, lll., assignor to International lVIinerals & Chemical Corporation, a corporation of New York Application January 28, 1957, Serial No. 636,691

2 Claims. (cl. 26o-527) This invention relates to a process for recovery of glutamic acid from glutamic acid mother substances. More particularly, it relates to a process for recovery of glutamic acid from sugar beet waste liquors, such as Steffens filtrate, containing glutamic acid precursor cornpounds, and for minimizing the loss of glutamic acid in the inorganic salts obtained as a by-product therefrom.

One process for the commercial production of glutamic acid involves the following steps. A Steifens ltrate is hydrolyzed under alkaline conditions, and the hydrolyzate is carbonated to separate calcium therefrom in theform of calcium carbonate, then concentrated to about 40% dry solids and acidilied to about pH 3.2 with sulfuric acid. lInorganic salts are precipitated thereby, and are filtered off. The filtrate is further concentrated to about 70% dry solids, and a second crop of inorganic salts is ltered olf at a temperature maintained above about 65 C. to minimize glutamic acid crystallization. The

and glutamic acid is crystallized therefrom. This process has a number of advantages, but it suffers from thev fact that glutamic acid tends to crystallize with the second crop of inorganic salts, from which it is not recovered in the process as heretofore practised, and the losses of glutamic acid become more and more severe as the quality of the starting material exceeds about 200 pounds of monosodium glutamate equivalent per ton of total solids, exclusive of calcium compounds yand the like.

The present invention is an improved glutamic acid recovery process employing alkaline hydrolysis of a sugar beet waste liquor and sulfuric acid acidulation of the hydrolyzate, coupled with certain critical operating and recycle features whereby the loss of glutamic acid in the inorganic salt cakes is minimized.

An object of the present invention is to recover glutamic acid from sugar beet waste liquors in improved yield.

Another object is to minimize the losses of glutamic acid in the inorganic salts and end liquors obtained as by-products in the treatment of sugar beet waste liquors.

Another object is to improve the recovery of glutamic acid from medium-grade Stefans liltrates.

These and other objects of the invention will be apparent from the following specification and claims.

My invention in a broad aspect is animprovement in the process for recovering glutamic acid from sugar beet waste liquors by alkaline hydrolysis, followed by sulfuric acid acidulation. In laccordance with my invenafter, and optimally certain acidic recycle liquors and/ or sulfuric acid, and by concentrating, if and to such extent obtained as by-products in the sugar beet industry foltion, a sugar beet waste liquor containing between about 200 and about 250 pounds of glutamic acid values, calculated as monosodium glutamate, per ton of dry solids, exclusive of calcium, barium or other alkaline-earth metal compounds, is hydrolyzed at elevated temperature with alkali. The hydrolyzate is adjusted to a pH betweenl as required. Inorganic salts are removed by filtration or the like, and the liquid phase further acidied with sulfuric acid to between about pH 2.5 and 3.5 and concentrated to a dissolved solids content of about 65 to about whereby a second crop of inorganic solids isk obtained with a substantial glutamic acid content. The solids are removed at a temperature above about 65 C. to minimize the quantity of glutamic acid therein. These solids are recycled to the hydrolyzate prior to or in conjunction with the rst acidulation. The liquid phase is diluted with water if necessary to a dissolved solids content around 60 to 80% by weight to repress the precipitation of further inorganic salts, then cooled to ordinary temperatures, and glutamic acid is crystallized therefrom. The crude glutamic acid is purified by conventional means. The volume of end liquor and the glutamic acid content thereof are materially lower than in the prior-art processes. 1

My invention is suitable in general for the treatment of sugar beet waste liquors containing glutamic acid pre-V cursor compounds equivalent to between about 200 and about 250 pounds of monosodium glutamate (MSGE) per ton of total solids, exclusive of barium, calcium, and other alkaline earth metal componnds (which are commonly removed in a separate step in advance of the other inorganic constituents). Liquors of lower quality with respect to MSGE content do not ordinarily giveV rise to any serious problem of glutamic acid losses in theinorganic cake, while liquors of higher quality lead to a continuing increase in quantity of the recycled inorganics cake if treated asin my invention. Among suitable types of liquors are Steifens filtrate, barium ltrate, and the like, and concentrates thereof, which are lowing the removal of sugar from beet molasses, and residual liquors from the fermentation thereof, such as vinasse, schlempe, citric acid fermentation residues, and the like Steifens filtrate refers to waste liquors remaining after the separation of sugar from beet molasses by precipitation as calcium saccharate. Similarly, barium filtrate refers to waste liquors remaining after the separation of sugar from beet molasses by precipitation as barium saccharate.

An advantageous embodiment of my invention is illustrated in the attached drawing. The said embodiment employs waste liquor from the Stelfens process as the starting material. This liquor contains around 2% by weight of total solids, and for most effective treatment in my process, it should contain between about 200 and 250 pounds of monosodium glutamate equivalent (i.e., potential glutamic acid, calculated as monosodium glutamate, and referred `to hereinafter as MSGE) per ton of total solids, exclusive of calcium compounds. In-

cluded in the solids are a sucient quantity of sodium hydroxide, potassium hydroxide, and calcium hydroxide to produce a pH between about 9 and about 12.5. 'I'he liquor, as it emerges from the Steffens process, is at a temperature around C., and the glutamic acid precursor compounds therein can be effectively hydrolyzed by storing the liquor for a period of time in an insulated vessel. The hydrolysis reaches a satisfactory level in from about 15 to about 120 hours, during which time the temperature will ordinarily drop to around 60 C.

' The hydrolyzate is contacted with a sufficient quantity of carbon dioxide to precipitate the calcium substantially completely therefrom in the form of calcium carbonate. The pH will thereby be reduced to less than about 12. The calcium carbonate precipitate is removed by filtration, centrifugation, or the like and is washed with water to recover any entrained glutamic acid values.

Patented Apr. 19, 1960 The combined-ltrate and wash Vwater are commngled with an inorganic saltcake containing glutamic acid, recycled from bination with organic substances, and acts in part-to-,acidulate thef'iltered; hydrolyzate;

quantity ofsulfuric acid is added to reduce the pI-Ifofthe"Y Y mixture 'to betweeniabout 5` andk about 9, preferably be'- tween` about 5.5 and about 6.5. Under-these conditions,A

the glutamic acid contained in the recycled inorganic salt cake is substantially completely redissolved. VThe mixture is then concentrated, preferably under vacuum, to a dissolved Vsolids content between about 40 and about 65% by weight, preferably between aboutY 50 and about 60%; I prefer to carry out the concentration at this point; alternatively, however, itY is` possible to carry out the concentration prior to addition of the` recycle cake, and/ or prior to any `further acidulation, although these are less advantageous embodiments of theinvention. A heavy slurry results from the concentration step, and is filtered or` centrifuged. The solids content can 4be somewhat higher, up to about 80%', if the separation of solids is carried out at elevatedYV temperatures, e.g., upV to 75 C. or higher. The inorganics cakeis1 washed with water-and rejected from the process. This cake contains littleV or no glutamic acid values.'

The filtrate is furtheracidifiedV to around pH 2.5-3;5,

n preferably aboutpI-Il, then-concentrated under reduced pressure to about 65 to about 86% dissolved solids, preferably around 80%. A second crop of inorganic salts is producedthereby, and is iiltered oi or centrifugedrwhile theVslurry is maintained` at a temperatureV above about 65 C. in; order to minimize crystallization of glutamic acid. These solidsfnevertheless contain a considerable proportion of glutamicacid, owing to the solubilities involved" in this system. lI have found that the glutamic acid values `thereincan be lsubstantially completely recovered fby recycling the entire 'cake'to'the hydrolyzate,

where the acid content Vthereof is expended to eiect part ofthe iirst Yacidulation to pH 5-9. By means of this recycle,` the glutamic acidvalues are redissolved and re- Af suflicient additional bonation and concentration, possesses suflicient alkalinity to produce a pH of about to about 12 or higher. If stored in an insulated vessel at the discharge temperature, around 95 C., it cools slowly, and simultaneously the glutamic acid mother substances undergo autohydrolysis. Nearly complete hydrolysis takes place in from about 3 to about 120 hoursV ata temperature between n' about 95 and about 55 C. Furtherhydrolysis may then be produced if desired by concentrating the hydrolyzate covered-,rand the inorganic salts are then rejected under conditionswhich avoid` entrainment of glutamic aeidj The'liquid phase'is thereupon diluted slightlyV with water, if and-asV required, to a dissolved solids content of aboutv 60'V tolaboutg80%, preferably about 60 to about 65%,"inorder to inhibit further crystallization of inorganicls'olids, and is'then cooled to ordinaryV temperav tures below about l35" C; The liquid may be seeded with glutamicacid crystals if desired, and glutamic acid crystallizes'therefrom in a periodof about l to about 6 days. i Theglutamic acid slurry is filtered or centrifuged to separate the crude glutamic acid, leaving an end liquor of decreased volume and glut-amic'acid content, corn-V pared with-the processes of the prior art.

The crude glutamic acid. is-puritied in a conventional manner; lIt is ordinarily rst repulped with a mother liquor obtained in the crystallization of purified glutamic acid, iltered, slurried in `water and adjusted top I-I 6-7 i 'withY` sodium hydroxide, Ytreated with decolorizing carbon, andV reacidiiied to pH 3.2, at which point purified glutamic Many modilications and alteracid readily crystallizes. native procedures are described in the prior art. n

`In another embodiment of the invention, thin barium ltrate is subjectedl to autohydrolysis, and the resulting hydrolyzate is treated as set forth hereinabove. Thin barium ltrate is the residual solutionremaining after the precipitation of sugar from sugar beet molasses as barium saccharate. water,V together with hydroxides of barium, sodium, and potassium, a quantity of'sugar and other carbohydrates,

Thin barium iltrate contains about 80%AV organicn acids, and nitrogenous substances, including. glutamic acidand glutamic acid mother-substances, such asf pyrrolidonecarboxylic acid. This material, as. discharged'from 4the desuganz/.ing` process and prior to carto a` dissolved solids content between about 40 and about.

% by weight. Alternatively, the autohydrolysis and the concentration may be carried out simultaneously.

The alkaline hydrolysis of my starting materialcan be carried o ut in accordance with any of the techniques described in the art; Thin Steiens filtrate or thin barium filtrate can "conveniently be subjected to autohydrolysis, as described above. Concentratedltrates containing, for example, from about 40 to about-65% solids-can` be hydrolyzed with4 potassium hydroxide or preferably sodium hydroxide, employing up to about 10% by weight thereof, preferably from about 4 to about 8% and heating at O to C. for 1 to 4 hours (e.g., 21/44 hours at 855C'. Y

yWhile the hydrolysis of sugar beet waste liquors can readily and effectively be carried out with strong caustic substances such as sodium hydroxide or potassium hydroxide, certain advantages attach to the use of the alkalineearth metal hydroxides vfor this purpose. A principal advantage lies inY theV factV that the alkaline-earth metals are conveniently removed from the hydrolyzate as insoluble salts such as the sulfate, the carbonate, the phosphate, the sulte, and the like, and thus lessen the problem Vof removing inorganic salts at later stages of the process. YFor thisipurposathe teaches that calcium hydroxidecan be employed.,VV l have found that barium hydroxide and'strontium'hydroxide can also lie-employed,

with superior results.. In theuse of the latter substances, 1t is advantageous to adjust the Vsolids concentration of .the waste liquor to between about 25 and about 55% by weight-for most effective hydrolysis. Between Vabout .5 andaboutV 25% by weight of the hydrolytic agent, based onlthe starting material, should be employed, and the mixture should be heated to a temperature between about 65 and about 100 C. for a period ranging between about 1 and about 8 hours, preferably around 85V C. for about 21/2 hours. The hydrolytic agent is then conveniently removed by cooling lthe hydrolyzate to about 60 C.,or

.lower andV treating with carbon dioxide toY adjust the p H toi a value, Vbetween about 8.0 and-about 12.0, at least as low as the; initial pH. of thewa'ste liquor. The resulting pHA will be between about 9.5 and about 10.5 in the, case of Steffens ltrates obtained from beets grown west of Vthe Rocky Mountains, and up to about 11.5 for Rocky filtrateY having a pH of 9 and containing 50% solids, in-

cluding 220 parts of monosodium glutamate equivalent per ton of total solids. All parts and percentages are by weight unless otherwise speciiied.

Example Theconcentrated Steiens filtrate (1000 parts) is hydrolyzed by; heating withr parts ofaqueous 50% sodium hydroxidersolution at 85 C. for 21/4 hours. The hydrolyzateV is cooled to roomY temperature, and to it are added'300'parts Vof crude glutamic" acid repulp water from a previous batch,jcontaning,5 partsof MSGEgjlSOparts of pH 3.2 inorganics cake from a previous batch, containing 30 parts of MSGE; and 150 parts of aqueous 50% sulfuric acid. The resulting mixture, having a pH of 6.0, is thoroughly agitated, then filtered, and the lter cake is Washed with 100 parts of water. The washed cake, containing 130 parts of dry solids, including 0.1 part of MSGE, is rejected from the process. Y

The iiltrate is acidied topH 3.2 with 230 parts of 50% sulfuric acid, then concentrated to 790 parts (approximately 78% solids content), and ltered rapidly at about 80 C. The iilter cake, containing 150 parts of dry solids, including 30 parts of MSGE, is recycled to the hydrolyzate in a succeeding batch.

The filtrate is diluted with 45 parts of Water` toV a' solids content of 70%, then cooled to room temperature, and allowed to stand for five days while crude glutamic acid crystallizes therefrom. The crude glutamic acid is i'lltered off, repulped with mother liquor from the filtration of purified glutamic acid in a subsequent step of a previous batch, and again ltered. The filtrate is recycled to the hydrolyzate in a succeeding batch. The glutamic acid cake is slurried with Water, adjusted to pH 6 with sodium hydroxide, decolorized with activated carbon, and reaciditied to pH 3.2 with sulfuric acid.V Purified glutamic acid is crystallized therefrom, filtered off, and dried. The mother liquor is recycled to repulp the crude glutamic acid from a succeeding batch. The dried purified glutamic acid weighs about 29 parts, corresponding to about 36.5 parts of MSGE.

After appropriate adjustments for recycle, the material balance in the foregoing process is as follows:

The foregoing example is submitted only to illustrate a preferred embodiment of the present invention, and in no Way as a limitation upon the scope thereof. Numerous modifications and equivalents of the invention will be apparent to those skilled in the art from the foregoing description. Y

In accordance With the present description, I claim as my invention:

1. A process for recovery glutamic acid from a sugar beet waste Water selected from the group consisting of Steifens ltrate and barium ltrate, said waste water containing glutamic acid values equivalent to between about 200 and about 250 pounds of monosodium glutamate per ton of total solids, exclusive of alkaline-earth metal compounds, which comprises hydrolyzing the glutamic acid precursors in said waste water at elevated temperature under alkaline conditions, commingling the hydrolyzate with a substance whereby any alkaline-earth compounds thereinV are converted into compositions insoluble in said hydrolyzate, separating said insoluble compositions therefrom, acidifying the hydrolyzate witn inorganic salts therefrom, acidifying the liquid phase with sulfuric acid to a pH between about 2.5 and about 3.5, concentrating to a dissolved solids content between about 65 and about 85% by weight, separating therefrom at a temperature above about 65 C. a mixture of inorganic salts containing sulfuric acid values and a substantial proportion of glutamic acid, recyclingvsaid mixture to said hydrolyzate for effecting, at least in part, said adjustment to a pH between about 5 and about 9, and for Yrecovering the glutamic acid values contained therein,

adjusting the liquid phase to a dissolved solids content between about and about 80% by weight by adding water thereto as required, cooling to a temperature below about 35 C., and crystallizing glutamic acid therefrom.

2. A process for recovering glutamic acid from a thin Steens filtrate containing glutamic acid values equivalent to Ibetween about 200 and about 250 pounds of monosodium glutamate per ton of total solids, exclusive of calcium compounds, which comprises hydrolyzing the glutamic acid precursors in said filtrate' at a temperature between about 60 and about 95 C. in the presence of the alkaline materials existing therein, precipitating calcium from the hydrolyzate with carbon dioxide and separating the resulting calcium carbonate therefrom, acidifying the hydrolyzate with sulfuric acid to a pH betweenl about 5 and 9, concentrating the hydrolyzate to a dissolved solids content between about 40 and about 65% by weight, separating inorganic salts therefrom, acidifying the liquid phase with sulfuric acid to a pH between about 2.5 and about 3.5, concentrating to a dissolved solids content between about and about 85 by Weight, separating therefrom at a temperature above about 65 C. a mixture of inorganic salts containing sulfuric acid values and a substantial proportion of glutamic acid, recycling said mixture to said hydrolyzate for effecting, at least in part, said adjustment to a pH between about 5 and about 9, and for recovering the glutamic acid values contained therein, diluting the `liquid phase to a dissolved solids content between about 60 and about 65% by weight, cooling to a temperature below about 35 C., and crystallizing glutamic acid therefrom.

References Cited in the iile of this patent UNITED STATES PATENTS 2,517,601 Shafor Aug. 8, 1950 2,535,117V Bennett Dec. 26, 1950 2,688,037 Hoglan Aug. 31, 1954 2,730,545 Hoglan Ian. 10, 1956 

1. A PROCESS FOR RECOVERY GLUTAMIC ACID FROM A SUGAR BEET WASTE WATER SELECTED FROM THE GROUP CONSISTING OF STEFFEN''S FILTRATE AND BARIUM FILTRATE, SAID WASTE WATER CONTAINING GLUTAMIC ACID VALUES EQUIVALENT TO BETWEEN ABOUT 200 AND ABOUT 250 POUNDS OF MONOSODIUM GLUTAMATE PER TON OF TOTAL SOLIDS, EXCLUSIVES OF ALKALINE-EARTH METAL COMPOUNS, WHICH COMPRISES HYDROLYZING THE GLUTAMIC ACID PRECURSORS IN SAID WASTE WATER AT ELEVATED TEMPERATURE UNDER ALKALINE CONDITIONS, COMMINGLING THE HYDROLYZATE WITH A SUBSTANCE WHEREBY ANY ALKALINE-EARTH COMPOUNDS THEREIN ARE CONVERTED INTO COMPOSITION INSOLUBLE IN SAID HYDROLYZATE, SEPARATING SAID INSOLUBLE COMPOSITIONS THEREFROM, ACIDIFYING THE HYDROLYZATE WITH SULFURIC ACID TO A PH BETWEEN ABOUT 5 AND 9, CONCENTRATING THE HYDROLYZATE TO A DISSOLVED SOLIDS CONCENTRATION BETWEEN ABOUT 40 AND ABOUT 65% BY WEIGHT, SEPARATING INORGANIC SALTS THEREFROM, ACIDIFYING THE LIQUID PHASE WITH SULFURIC ACID TO A PH BETWEEN ABOUT 2.5 AND ABOUT 3.5, CONCENTRATING TO A DISSOLVED SOLIDS CONTENT BETWEEN ABOUT 65 AND ABOUT 85% BY WEIGHT, SEPARATING THEREFORM AT A TEMPERATURE ABOVE ABOUT 65*C. A MIXTURE OF INORGANIC SALTS CONTAINING SULFURIC ACID VALUES AND A SUBSTANTIAL PROPORTION OF GLUTAMIC ACID, RECYCLING SAID MIXTURE TO SAID HYDROLYZATE FOR EFFECTING, AT LEAST IN PART, SAID ADJUSTMENT TO A PH BETWEEN ABOUT 5 AND ABOUT 9, AND FOR RECOVERING THE GLUTAMIC ACID VALUES CONTAINED THEREIN, ADJUSTING THE LIQUID PHASE TO A DISSOLVED SOLIDS CONTENT BETWEEN ABOUT 60 AND ABOUT 80% BY WEIGHT BY ADDING WATER THERETO AS REQUIRED, COOLING TO A TEMPERATURE BELOW ABOUT 35*C. AND CRYSTALLIZING GLUTAMIC ACID THEREFROM. 